Introduction: The most common cause of adult Giant Hydronephrosis (GH) is congenital Uretero-Pelvic Junction (UPJ) obstruction. Conventional imaging modalities, like Intravenous Urography (IVU) and Computed Tomography Urography (CTU) and radionuclide renal scan can be fallacious. Serum carbohydrate antigen 19-9 (CA19-9) is a useful tumour marker for gastrointestinal and pancreatic cancer. Only a few studies and case reports have shown raised serum levels due to benign hydronephrosis and GH.

Aim: To investigate the prognostic role of urine and serum CA19-9 in the diagnosis and follow-up of adult GH due to UPJ obstruction.

Materials and Methods: The present hospital based observational study was conducted on 24 adult patients (Group 1) with unilateral GH due to UPJ obstruction. Twenty four healthy adults were included as control (Group 2). Serum and voided urine samples were collected to evaluate Carbohydrate Antigen (CA) 19-9 in each group. During surgery, urine from the affected pelvis was collected to determine CA19-9 level. Patients were followed up after surgery at 3 and 9 months with serum and voided urine samples for CA19-9 level.

Conclusion: Voided urine CA19-9 can be a non-invasive clinical marker in adult GH due to UPJ obstruction. The clinical implications of these data for diagnosis and follow-up of these patients are significant. Our findings suggest, significant decrease in urinary Ca19-9 level during follow-up is predictive of excellent surgical outcome and resolution of renal damage.